Electric, plug-in, battery, and hybrid electric vehicles (HEVs) have a powertrain that includes, among other components, an internal combustion engine, an electric machine or motor/generator, and a battery that are coupled with one or more controllers, current and voltage sensors, and switching components that couple and decouple the battery from other vehicle components. Such components are configured to estimate a state of charge (SoC) of the battery using various current integration techniques that may be undesirably affected by noise in current signals having zero or near zero magnitudes. HEVs may benefit from more accurate SoC estimation capabilities, which may further improve battery lifespan, durability, and performance, and which may in turn enable improved SoC monitoring, adjustment, and control of battery.